Safety device for catalytic converter

ABSTRACT

Safety devices prevent packaged catalytic converters from being expelled from stacks, or at least reduce the velocity with which such a package may be expelled, in case of an explosion in a bio-fueled appliance, such as a wood-burning stove.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/622,606, filed Jun. 14, 2017, titled “Safety Device for CatalyticConverter” (now U.S. Pat. No. 10,001,276, issued Jun. 19, 2018), whichis a continuation of U.S. patent application Ser. No. 13/914,832, filedJun. 11, 2013, titled “Safety Device for Catalytic Converter” (now U.S.Pat. No. 9,709,267, issued Jul. 18, 2017), which claims the benefit ofU.S. Provisional Patent Application No. 61/658,749, filed Jun. 12, 2012,titled “Safety Device for Catalytic Converter,” the entire contents ofeach of which are hereby incorporated by reference herein, for allpurposes.

TECHNICAL FIELD

The present invention relates to catalytic converters for biofuel-firedboilers and, more particularly, to safety devices for such catalyticconverters.

BACKGROUND ART

United States Environmental Protection Agency (EPA) regulations limitthe amount of particulate matter, measured in grams per hour, that maybe emitted by a woodstove or wood-fired boiler. Catalytic converters arefrequently used to clean wood-fired exhaust. A catalytic converteressentially burns unburned fuel (smoke) from the fire before it exits aflue (smoke stack).

Conventional catalytic converters often include ribbons of metal,typically thin (such as about 0.004 inch thick) stainless steel, thatare coated with one or more catalysts. The ribbons are often corrugatedor “herringbone” shaped and then wound into spirals or folded back andforth. The wound or folded ribbons are then bound, such as by stainlesssteel rings, to maintain a desired shape (typically round) and diameter(slightly less than the inside diameter of a smoke stack). Each ring hasan upper lip and a lower lip to prevent the wound or folded ribbon fromsliding out of the ring. A ring with one or more such ribbons isreferred to herein as a packaged catalytic converter.

One or more such packaged catalytic converters may be placed inside astack, such that the axis of each ring is aligned with the central axisof the stack. The ribbons are oriented such that their surfaces areparallel with the axis of the stack and, therefore, with the directionof flow of the smoke.

The outside diameter of a packaged catalytic converter is typicallyslightly less than the inside diameter of a stack to facilitateinstalling the catalytic converter into the stack and to accommodatethermal expansion of the ring. Sometimes the gap between the outsidediameter of the ring and the inside diameter of the stack is packed witha compressible heat-resistant sealant. Consequently, smoke is preventedfrom passing around the packaged catalytic converter and, instead,passes over the surfaces of the ribbons. The sealant typically does not,however, provide much structural fixation of the ring to the stack.

A typical packaged catalytic converter weighs about 5 pounds, althoughthe weight can vary, based on its diameter, length, material thickness,etc. Nevertheless, a typical packaged catalytic converter has asubstantial mass packed into a relatively small volume, and the package(ring) has a hard outer surface.

Occasionally, small or large explosions occur within wood-burningappliances, particularly in gasification appliances. Such an explosioncan propel a packaged catalytic converter out of the stack. Essentially,the stack becomes a canon barrel, and the packaged catalytic converterbecomes a projectile. Catalytic converter packages have been known to beprojected about 25 feet into the air above a wood-burning appliance. Ahot catalytic converter package ejected from a stack can cause a fire ifit lands on dry grass, a wood shingled roof or other flammable material.Furthermore, a falling catalytic converter can injure a person or animalor cause impact damage to property. Catalytic converter packagesdisposed within stacks can, therefore, pose safety problems.

SUMMARY OF EMBODIMENTS

An embodiment of the present invention provides a safety device for acatalytic converter. The safety device includes a smoke pipe. The smokepipe is configured to be attachable to an exhaust from a bio-fuel firedappliance. The smoke pipe includes a wall. The wall defines a pluralityof apertures (ports) through the wall of the smoke pipe.

Optionally, at least a first portion of the plurality of apertures isdefined along a first line parallel to a longitudinal axis of the smokepipe.

A second portion of the plurality of apertures may be defined along asecond line. The second line may be spaced apart from, and parallel to,the first line. The apertures of the second portion of the plurality ofapertures may be staggered along the second line, with respect to theapertures of the first portion of the plurality of apertures.

Each aperture may have a diameter of about ½ inch to about 3 inches.

The smoke pipe may include an inside wall that defines an interior. Thesafety device may also include at least one first bar attached to thesmoke pipe. The at least one first bar extends inward of the inside walland at least partially into the interior of the smoke pipe. The at leastone first bar may be spaced at least about 6 inches away from itsnearest aperture, as measured along a longitudinal axis of the smokepipe.

The safety device may also include at least one second bar attached tothe smoke pipe and extending inward of the inside wall of the smoke pipeand at least partially into the interior. The apertures are locatedbetween the first at least one bar and the second at least one bar, asviewed along the longitudinal axis of the smoke pipe. The at least onesecond bar may be spaced at least about two feet away from its nearestaperture, as measured along the longitudinal axis of the smoke pipe.

The safety device may also include a catalytic converter disposed in theinterior of the smoke pipe, between the at least one first bar and theat least one second bar.

At least one of the first bars may include a temperature sensor.

Another embodiment of the present invention provides a safety device fora catalytic converter. The safety device includes a catalytic converterconfigured for disposition within an interior of a smoke pipe extendingfrom a stationary bio-fuel fired device. The safety device may alsoinclude a bracket hingedly attached to the catalytic converter. Thebracket may be configured to be attached to an interior wall of thesmoke pipe. Once the bracket is attached to the interior wall, thecatalytic converter is hingedly attached to the interior wall.

The safety device may also include the smoke pipe. The bracket may beattached to the interior wall of the smoke pipe.

Yet another embodiment of the present invention provides a safety devicefor a catalytic converter. The safety device includes a smoke pipe. Thesmoke pipe has an inlet, an outlet and a middle portion between theinlet and the outlet. The inlet defines an internal cross-sectionalarea, and the outlet defines an internal cross-sectional area. Themiddle portion defines an internal cross-sectional area greater than theinlet internal cross-sectional area and greater than the outlet internalcross-sectional area.

The middle portion may define an internal cross-sectional area greaterthan twice the inlet internal cross-sectional area.

The smoke pipe may include an inside wall and define an interior. Thesafety device may also include at least one first bar attached to thesmoke pipe and extending inward of the inside wall and at leastpartially into the interior. The number of bars and their positionswithin the interior may be selected so as to define no space within theinterior through which an object having a dimension equal to the largestinside diameter of the inlet can pass from the from the inlet to theoutlet.

The safety device may include a second smoke pipe that includes aninside wall defining an interior. The second smoke pipe may be incommunication with the inlet. At least one second bar may be attached tothe second smoke pipe and extend inward of the inside wall and at leastpartially into the interior.

A catalytic converter may be disposed in the interior of the secondsmoke pipe, between the at least one first bar and the at least onesecond bar.

An embodiment of the present invention provides a safety device for acatalytic converter. The safety device includes a smoke pipe thatincludes an inside wall and that defines an interior. At least one firstbar is attached to the smoke pipe and extends inward of the inside walland at least partially into the interior. At least one second bar isattached to the smoke pipe and extends inward of the inside wall and atleast partially into the interior. The at least one second bar isdisposed a distance away from the at least one first bar, as measuredalong a longitudinal axis of the smoke pipe. At least one third bar isattached to the smoke pipe and extends inward of the inside wall and atleast partially into the interior. The at least one third bar isdisposed between the at least one first bar and the at least one secondbar. The at least one third bar is laterally off-center within theinterior.

The safety device may also include a catalytic converter disposed in theinterior, between the at least one second bar and the at least one thirdbar.

Another embodiment of the present invention provides a method formitigating damage caused by a catalytic converter driven within a smokepipe as a result of an explosion. The method includes attaching a cap toan exhaust end of the smoke pipe. The cap is configured to withstand anexpected impact from the driven catalytic converter as a result of theexplosion.

Optionally, the method may include attaching at least one bar to thesmoke pipe, such that the at least one bar extends inward of an insidewall and at least partially into an interior of the smoke pipe. The atleast one bar is disposed at least four feet from the cap, as measuredalong a longitudinal axis of the smoke pipe.

The cap may include a pivoted portion.

Yet another embodiment of the present invention provides a catalyticconverter package. The catalytic converter package includes a tubedefining an interior. One end of the tube defines a tube opening havingan inside diameter. An inwardly-oriented lip is attached along at leasta portion of a circumference proximate the other end of the tube. Thelip defines a lip opening into the interior of the tube. The lip openinghas an inside diameter less than the inside diameter of the tubeopening. A catalyst is configured to promote combustion of at least someexhaust from a bio-fuel fire. The catalyst is releasably disposed withinthe interior of the tube. The catalyst is configured, as disposed in theinterior of the tube, to have an outside diameter larger than the insidediameter of the lip opening, but less than the inside diameter of thetube opening. The catalyst is releasable out the tube opening, withoutaltering the outside diameter of the catalyst.

The catalyst may include a spiral-wound ribbon.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more fully understood by referring to thefollowing Detailed Description of Specific Embodiments in conjunctionwith the Drawings, of which:

FIG. 1 is a perspective view of a typical conventional wound catalyticconverter ribbon, according to the prior art.

FIG. 2 is a perspective view of a typical conventional packagedcatalytic converter, according to the prior art.

FIG. 3 is a schematic longitudinal cross-sectional view of the packagedcatalytic converter of FIG. 2.

FIG. 4 is a schematic longitudinal cross-sectional view of awood-burning appliance coupled to a stack that is equipped with apackaged catalytic converter, according to the prior art.

FIG. 5 is a schematic longitudinal cross-sectional view of awood-burning appliance coupled to a stack that is equipped with apackaged catalytic converter and a safety device, according to anembodiment of the present invention.

FIG. 6 is a schematic longitudinal cross-sectional view of a hingedsafety device, according to another embodiment of the present invention.

FIG. 7 is a schematic longitudinal cross-sectional view of a portion ofa stack having an enlarged section safety device, according to yetanother embodiment of the present invention.

FIG. 8 is a schematic longitudinal cross-sectional view of a stackequipped with a packaged catalytic converter and a safety device,according to another embodiment of the present invention.

FIGS. 9 and 10 are schematic longitudinal cross-sectional views of twostacks equipped with safety device caps, according to two otherembodiments of the present invention.

FIG. 11 is a perspective view of a packaged catalytic converter with anintegral safety device, according to yet another embodiment of thepresent invention.

FIG. 12 is a schematic longitudinal cross-sectional view of the packagedcatalytic converter of FIG. 11.

FIG. 13 is a schematic longitudinal cross-sectional view of a stackequipped the packaged catalytic converter of FIGS. 11 and 12, after thecatalytic converter deployed the safety device.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

In accordance with preferred embodiments of the present invention,methods and apparatus are disclosed for preventing a packaged catalyticconverter from being expelled from a stack, or at least reducing thevelocity with which such a package may be expelled, in case of anexplosion in a bio-fuel fired appliance or the like.

Bio-fuel here means a fuel that is in some way derived from biomass,including solid biomass, liquid fuels and bio-gases. Biomass, arenewable energy source, is biological material from living, or recentlyliving, organisms, such as wood, waste, algae, (hydrogen) gas andalcohol fuels. Exemplary solid biofuels include wood and wood pellets.Bioethanol is an alcohol made by fermenting sugar components of plantmaterials; it is made mostly from sugar and starch crops. Someembodiments of the present invention may be used with conventionalfossil fuels, such as coal, oil or oil-derived fuels. Thus, whereappropriate, the term bio-fuel includes fossil fuels.

FIG. 1 is a perspective view of a typical conventional wound catalyticconverter ribbon 100, and FIG. 2 is a perspective view of a typicalconventional packaged catalytic converter 200 that includes a ring 202and a ribbon 100. FIG. 3 is a schematic longitudinal cross-sectionalview of the packaged catalytic converter 200. As can be seen mostclearly in FIG. 3, the ring 202 includes an upper lip 300 and a lowerlip 302 that retain the wound or folded ribbon 100 within the ring 202,i.e., the lips 300 and 302 prevent the ribbon 100 from sliding up ordown out of the ring 202. I refer to the shape of the ring 202 shown inFIG. 3 as “C-shaped” (in cross section), and I refer to the ring 202 asa “C-shaped ring.”

When the packaged catalytic converter 200 is placed in a stack, smoke304 enters via an opening 306 defined by the lower lip 302. The smokepasses over the surfaces of the ribbon 100 and then exits via a secondopening 308 defined by the upper lip 300. The ribbon 100 typicallyincludes a catalytic material adhered to the surface of the ribbon.Components of smoke coming in contact with the catalytic material arecombusted, thereby cleaning the smoke.

FIG. 4 is a schematic longitudinal cross-sectional view of awood-burning appliance 400 coupled to a stack 402 that is equipped witha packaged catalytic converter 200, according to the prior art. If anexplosion occurs in the wood-burning appliance 400, the packagedcatalytic converter 200 may be expelled with great velocity out of thestack 402, as indicated by arrow 404. Clogged catalytic converters aremore susceptible to expulsion, because they present more resistance togas flow than clean catalytic converters. As noted, such explosions havebeen known to cause catalytic converter packages to be projected up toabout 25 feet in the air. A flying catalytic converter can create ahazard to people, animals and property, especially because the ejectedcatalytic converter is likely to be very hot (on the order of severalhundred degrees Fahrenheit), and where such a projected catalyticconverter lands is unpredictable.

Embodiments of the present invention prevent packaged catalyticconverters from being expelled from stacks, or at least reduce thevelocity with which such a package may be expelled. FIG. 5 is aschematic longitudinal cross-sectional view of an embodiment of thepresent invention. In this embodiment, the stack 500 includes a wallthat defines a plurality of holes (ports) 502 through the wall andpositioned a distance 504 above the height of the catalytic converter200. In case of an explosion that drives the catalytic converter 200 upthe stack 500, once the catalytic converter 200 is driven above theheight of the ports 502 (as shown in dashed line at 200′), pressure offrom the explosion is vented out of the stack 500 by the ports 502,thereby reducing or eliminating the force driving the catalyticconverter 200.

Optionally, one or more bars 506 (“top bars”) may extend into theinterior of the stack 500 to stop the catalytic converter 200 fromtranslating further up the stack 500. The top bars 506 should be locateda sufficient distance 508 above the ports 502 to enable the catalyticconverter 200 to be driven completely above the ports 502, therebypreventing a driven catalytic converter 200 from blocking the ports 502.The top bars 506 may extend only partially into the interior of thestack 500, as shown in the lateral cross-sectional view in FIG. 5, orsome or all of the top bars 506 may extend all the way across theinterior (not shown) of the stack 500. In some embodiments, temperature,oxygen or other sensors used by a control system may act as some or allof the top bars 506. The bars should be made of a corrosion-resistantmaterial, such as stainless steel.

After pressure in the stack 500 returns to normal, the catalyticconverter 200 may fall back down the stack 500 due to the force ofgravity. Optionally, additional bars 510 (“bottom bars”) may be disposedin the interior of the stack 500 to define a bottom position for thecatalytic converter 200. If the catalytic converter 200 falls back downthe stack 500, the bottom bars 510 limit the downward translation of thecatalytic converter 200. As with the top bars 506, the bottom bars 510may extend partially or fully through the interior of the stack 500.However, fewer or smaller in diameter bottom bars 510 may be needed thantop bars 506, because the force of an explosion is likely to cause thecatalytic converter 200 to strike the top bars 506 with greater forcethan gravity will cause the catalytic converter 200 to strike bottombars 510. In some embodiments, temperature, oxygen or other sensors usedby a control system may act as some or all of the bottom bars 510. Thetop bars 506 and the bottom bars 510 form respective stops for travel ofthe catalytic converter 200 within the stack 500.

Optionally, the stack 500 includes sections of smoke pipe that may beassembled end-to-end to form a desired length of stack, in a well-knownmanner. The stack 500 may include a joint 511 between two such sectionsto facilitate inserting the catalytic converter 200. Optionally oralternatively, some or all of the top and/or bottom bars 506 and/or 510may be threaded or otherwise configured to be removable and replaceablethrough the wall of the stack 500.

In some embodiments, about seven one-inch diameter ports 502 are definedat least about two feet, preferably about four to eight feet, above thenormal position of the catalytic converter 200. Preferably, the ports502 are arranged in two or more staggered rows, and each row is alignedwith the longitudinal axis of the stack 500, i.e., the direction inwhich the catalytic converter 200 would be translated in case of anexplosion. For large stacks 500, such as stacks larger than about12-inches in diameter, or if a large explosion is possible, more and/orlarger ports 502, possibly arranged in more rows, may be defined in thestack 500. Conversely, smaller and/or fewer ports 502 may be used insmaller stacks 500. Ports 502 having diameters between about one-halfinch and about three inches may be used in various embodiments.Successive ports 502 may be relatively closely spaced, such as withinabout one port diameter of the respective preceding port. The number,and/or size and/or spacing of the ports 502 should be selected based onexpected pressure inside the stack 500 in case of an explosion.

Under normal operating conditions, a draft inside the stack 500 resultsin negative pressure at the ports 502, as measured outside the stack500. Thus, under normal operating conditions, smoke should not exit thestack 500 through the ports 502. However, to prevent the possibility ofsmoke entering a space occupied by the stack 500, and to prevent(possibly heated) air in the space occupied by the stack 500 from beingdrawn into the ports 502 and up the stack 500, the ports 502 may besealed with light-weight material, such as foil or a suitablehigh-temperature polyester film, attached to the stack 500. The sealsshould be configured such that the force of an explosion easily burststhe seals blocking all or most of the ports 502.

One embodiment of such a seal 512 is shown in the left side of thedetail view in FIG. 5. In this embodiment, the seal 512 may be adheredto the outside surface of the stack 500, so as to prevent low-pressuregas from leaking into or out of the port 502. In other embodiments, theseal may be adhered to the inside surface of the stack 500, or the sealmay be attached intermediate the outside and inside surfaces of thestack 500.

Optionally or alternatively, a resilient flap 514 may be attached to theoutside surface of the stack 500, as shown in the right side of thedetail view in FIG. 5. In its normal position, the flap 514 covers itsrespective port 502, but during an explosion, the resilience of the flap514 enables the flap 514 to lift and allow explosion gas to escape viathe port 502. After the pressure in the stack 500 returns to normal, theresilience of the flap 514 causes the flap to return to its originalposition. In some embodiments, absent unusually high pressure inside thestack 500, the flap's resilience forces the flap into sealing engagementwith the exterior surface of the stack 500. “Resilient” here meansspringing back into shape, position, etc., elastic, storing energy of astrained material.

Although muzzle brakes are known in the gun, rifle and artillery arts,gun barrel ports are used for an entirely different purpose than theports 502 described herein. Gun barrel ports are used to reduce recoiland/or muzzle rise as a result of firing a weapon. Gun barrels aredesigned to project bullets, etc. In contrast, smoke stacks are notdesigned to project catalytic converters, and such action is highlyundesirable. Gun barrel ports would be useless if they releasedsufficient gas pressure to prevent a fired bullet from exiting thebarrel with sufficient velocity to travel a great distance. On the otherhand, my ports 502 are designed to do exactly the opposite of gun ports,i.e., my ports 502 are designed to release sufficient gas pressure toprevent a catalytic converter from being ejected from a stack, or atleast significantly reducing the velocity of such an ejection. Thus, ifanything, the gun, rifle and artillery arts teach away from my ports502.

FIG. 6 is a schematic longitudinal cross-sectional view of anotherembodiment of the present invention. A packaged catalytic converter 600is mounted in a stack 602 via a hinge, such as a pin, 604, preferablymade of stainless steel or another corrosion resistant material. Duringnormal operation, the catalytic converter 600 occupies the positionshown in solid line. However, if an explosion causes a sudden force 606to be exerted on the catalytic converter 600, the catalytic converter600 pivots about the hinge 604, such as to a position shown in dashedline. Once the force 606 ceases, gravity urges the catalytic converter600 to pivot back to its original position.

FIG. 7 is a schematic longitudinal cross-sectional view of yet anotherembodiment of the present invention. A packaged catalytic converter 700is disposed in a stack 702. The stack 702 defines an enlarged portion703 that has an inlet 704 and an outlet 705. The enlarged portion 703has a larger inside diameter 706 than the inside diameter of the inlet704 or the outlet 705. More specifically, the enlarged portion 703 has alarger inside diameter 706 than the inside diameter of the portion 707of the stack 702 in which the catalytic converter 700 is disposed undernormal operation. The enlarged portion 703 has a larger cross-sectionalarea than the inlet 704, the outlet 705 or the portion 707 of the stack702.

Thus, in case the catalytic converter 700 is driven up the stack 702 byrushing gas from an explosion, after the catalytic converter 700 reachesthe enlarged portion 703 of the stack 702 (as shown in dash line at700′), the gas bypasses the catalytic converter 700′, as indicated byarrows 708, thereby relieving pressure on the catalytic converter 700′.After the pressure of the gas subsides, the catalytic converter 700 mayfall back into its original position, or at least back to the bottom ofthe enlarged portion 703.

In some embodiments, the cross-sectional area of the enlarged portion703 is at least twice as large as the cross-sectional area of the inlet704, so even if the catalytic converter 700′ is completely clogged andit is driven into the enlarged portion 703, the availablecross-sectional area in the enlarged portion 703 remains at least equalto the cross-sectional area of the stack 702.

Optionally, one or more top bars 710 are disposed within the interior ofthe enlarged portion 704 of the stack 702 to inhibit the catalyticconverter 700 from reaching the top portion of the enlarged portion 703,or at least from exiting the enlarged portion 703. Preferably, theenlarged portion 703 and the top bars 710 are sized and configured suchthat, if the catalytic converter 700 is driven up against the top bars710, the remaining cross-sectional area 712 around the catalyticconverter 700′ is at least as great as the cross-sectional area of theportion 707 of the stack 702. The top bars 710 therefore preserve enoughcross-sectional area of the enlarged portion 703 to allow the explosiongas to bypass the catalytic converter 700′. Although all the top bars710 are shown in FIG. 7 as lying in a single plane, in otherembodiments, the top bars 710 may lie in more than one plane.

In general, there are enough top bars 710, and they are positionedwithin the interior of the enlarged portion 703, so as to define nospace within the interior, i.e., between the top bars 710, or betweenthe top bars 710 and the inside wall of the enlarged portion 703,through which the catalytic converter 700′ can pass. Generally, thecatalytic converter has a diameter slightly less than the insidediameter of the stack 702 and the inside diameter of the inlet 704. Ofcourse, the stack 702 and the inlet 704 may have shapes other thancircular. In any case, there are enough top bars 710, and they arepositioned within the interior of the enlarged portion 703, so as todefine no space within the interior through which an object having adimension equal to the largest inside diameter of the inlet 704 can passfrom the inlet 704 to the outlet 705.

Other aspects of the top bars 710 are similar to the top bars 506discussed above, with respect to FIG. 5. Bottom bars 714 may also beincluded, as discussed above, with respect to FIG. 5

FIG. 8 is a schematic longitudinal cross-sectional view of anotherembodiment of the present invention. A packaged catalytic converter 800is disposed in a stack 802 as shown in solid line. One or more top bars,preferably made of stainless steel or another corrosion resistantmaterial, exemplified by bars 804 and 805, extend at least part waythrough the interior volume of the stack 802. The bars 804-805 arepositioned, relative to the catalytic converter 800, such that if thecatalytic converter 800 is driven up, the catalytic converter 800strikes at least one of the bars 804-805, causing the catalyticconverter 800 to pivot as shown by arrow 806. For example, at least oneof the bars 805 may be disposed a lateral distance 808 off-center withinthe stack 802, as shown in the lateral cross-sectional view in FIG. 8.One or more of the bars 804-805 (such as top bar 804) or a separategrate (not shown), also preferably made of stainless steel or anothercorrosion resistant material, is positioned so as to prevent thecatalytic converter 800 from traveling further up the stack 802. Oncethe catalytic converter 800 has pivoted, gas can bypass the catalyticconverter 800, as indicated by arrows 810. After the pressure of the gassubsides, the catalytic converter 800 may fall back into its originalposition. Bottom bars 812 may be included to facilitate the catalyticconverter 800 returning to its original position, as discussed abovewith respect to FIG. 5.

Optionally or alternatively, a single bar may be bent so one portion ofthe bent bar is disposed as shown for bar 804 and another portion of thebar is disposed as shown for bar 805. In this context, the two portionsof the bar are referred to herein as separate bars. Optionally oralternatively, the bars 804-805 may be replaced by a grate (not shown)shaped and positioned to cause the catalytic converter 800 to pivot andstop traveling up the stack 802, as described with respect to the bars804. In this context, a bar herein means a bar or a grate.

Optionally or alternatively, as shown in FIG. 9, the stack 900 may beequipped with a cap 902. In most cases, the cap 902 prevents thecatalytic converter 904 from being ejected from the stack 900, in caseof an explosion. Instead, the catalytic converter 904 strikes the bottomof the cap 902 (as shown in dashed line at 904′). Once the catalyticconverter 904′ is out of the stack 900, explosion gas may easily escape,as indicated by arrows 906. Eventually, the catalytic converter 904′ mayfalls back down the stack 900, possibly as far as its original position.The top of the stack 900 may be flared to facilitate re-entry by thecatalytic converter 904′. Bottom bars 908 may be included, as discussedabove with respect to FIG. 5.

Even if the catalytic converter 904 is driven by an explosion withsufficient force to break through the cap 902 or to dislodge the cap 902from the stack 900, the moving catalytic converter 904 loses some energywhen it strikes the cap 902, thereby slowing the catalytic converter 904and reducing the likelihood that the catalytic converter 904 will exitthe stack 900 with great velocity and cause damage. However, the cap 902is preferably configured to withstand an expected impact from the drivencatalytic converter 904 as a result of an explosion, without allowingthe driven catalytic converter 904 to exit the stack 900 or dislodge thecap 902 from the stack 900. For example, the cap 902 may be fixed to thetop of the stack 900 with fasteners, rather than merely friction-fit tothe top of the stack 900. Preferably, the normal position of thecatalytic converter 904 is a distance 910 of at least about four feetfrom the cap 902, although other distances may be used.

FIG. 10 is a schematic longitudinal cross-sectional view of yet anotherembodiment of the present invention. A packaged catalytic converter 1000is disposed in a stack 1002. The stack 1002 is equipped with a pivotedcap 1004. The cap 1004 pivots about a hinge, such as a pin, 1006. In thenormal operating position of the cap (shown in solid line), the capallows smoke to exit the stack 1002, as indicated by arrow 1008.However, in case of an explosion that drives the catalytic converter1000 up the stack and causes the catalytic converter 1000 to strike thecap 1004, the cap 1004 pivots, as shown by arrow 1010, such as to theposition shown in dashed line. Pivoting the cap 1004 causes thecatalytic converter 1000 to lose some energy, possibly preventing thecatalytic converter 1000 from exiting the stack 1002. Thus, in mostcases, the cap 1004 prevents the catalytic converter 1000 from beingejected from the stack 1002, in case of an explosion. Instead, thecatalytic converter 1000 strikes the bottom of the cap 1004 and mayeventually fall back down the stack 1002, possibly as far as itsoriginal position. Bottom bars 1012 may be included, as discussed abovewith respect to FIG. 5.

Even if the catalytic converter 1000 is driven by an explosion withsufficient force to pivot the cap 1004 to a fully-open position or todislodge the cap 1004 from the stack 1002, the moving catalyticconverter 1000 loses some energy when it strikes the cap 1004, therebyslowing the catalytic converter 1000 and reducing the likelihood thatthe flying catalytic converter 1000 will cause damage. Preferably, thenormal position of the catalytic converter 1000 is a distance 1014 atleast about four feet from the cap 1004, although other distances may beused.

FIG. 11 is a perspective side view, and FIG. 12 is a schematiclongitudinal cross-sectional view, of a packaged catalytic converter1100, according to another embodiment of the present invention. Thepackaged catalytic converter 1100 includes a ring 1102 with a bottominwardly-oriented lip 1104 to prevent a wound or folded ribbon 1006 fromfalling out the bottom of the ring 1102, while the ring is in place in astack (not shown). The outside diameter 1008 of the wound or foldedribbon 1006 is larger than the inside diameter 1010 of an openingdefined by the lip 1104. However, the ring 1102 does not include a toplip. I refer to the shape of the ring 1102 shown in FIG. 11 as an“L-shape” (in cross section), and I refer to the ring 1102 as an“L-shaped ring.” Thus, in case of an explosion below the catalyticconverter 1100, instead of ejecting the entire packaged catalyticconverter 1100 from a stack, the ribbon 1006 may be ejected from thering 1102. Ejecting the ribbon 1006 from the ring 1102 reduces theresistance to gas flow presented by the catalytic converter 1100. Thus,the ring 1102 may remain in place or at least not translate as far upthe stack as would a conventional packaged catalytic converter.

I refer to the ring 1102 as having two ends, namely a bottom end 1112,from which the lip 1104 extends, and a top end 1114, which has no lip.The ring 1102 can also be referred to as a tube with two ends. Althougha circular cross-sectional ring 1102 has been described, the ring may beformed in other cross-sectional shapes, such as to match cross-sectionalshapes of interiors of stacks or mounting brackets within stacks.

Many prior art packaged catalytic converters include rivets, wires orother structures to bind the ribbons and prevent the ribbons fromunwinding. However, preferably, the ribbon 1006 is not bound, except bythe ring 1102.

As shown in FIG. 13, an ejected ribbon 1300 is very likely to uncoil orunfold within a stack 1302. Uncoiling of the ribbon 1300 absorbs some ofthe energy of the explosion. In addition, the uncoiled ribbon 1300 islikely to become less tightly packed, therefore present less resistanceto the flow of gas in the stack 1302. Consequently, the gas exerts lessforce tending to eject the uncoiled ribbon 1300 from the stack 1302.Furthermore, much of the uncoiled ribbon 1300 is likely to come intocontact with the inside surface of the stack 1302. Friction from thiscontact inhibits translation of the uncoiled ribbon 1300 further up thestack 1302. It should be noted that, even if the ribbon 1300 is ejectedfrom the ring 1102, while the ribbon 1300 remains in the stack 1302, theribbon 1300 continues to function as a catalyst for smoke passingthrough the stack 1302.

The cap 902 and/or the cap 1004, described above, may be used incombination with any of the other embodiments described above.Similarly, the other embodiments may be combined. For example, theembodiments shown in FIGS. 5 and 7 may be combined.

While specific values chosen for some embodiments are recited, it is tobe understood that, within the scope of the invention, values of all ofparameters may vary over wide ranges to suit different applications.

While the invention is described through the above-described exemplaryembodiments, it will be understood by those of ordinary skill in the artthat modifications to, and variations of, the illustrated embodimentsmay be made without departing from the inventive concepts disclosedherein. Furthermore, disclosed aspects, or portions of these aspects,may be combined in ways not listed above. Accordingly, the inventionshould not be viewed as being limited to the disclosed embodiments.

What is claimed is:
 1. A catalytic converter package, comprising: a tubedefining an interior, one end of the tube defining a tube opening havingan inside diameter; an inwardly-oriented lip attached along at least aportion of a circumference proximate the other end of the tube, the lipdefining a lip opening into the interior of the tube, the lip openinghaving an inside diameter less than the inside diameter of the tubeopening; and a catalyst configured to promote combustion of at leastsome exhaust from a bio-fuel fire, releasably disposed within theinterior of, and unbound to, the tube, and configured, as disposed inthe interior of the tube, to have an outside diameter larger than theinside diameter of the lip opening, and less than the inside diameter ofthe tube opening, such that the catalyst is releasable out the tubeopening without altering the outside diameter of the catalyst.
 2. Acatalytic converter according to claim 1, wherein the catalyst comprisesa spiral-wound ribbon.